1. Field of the Invention
The present invention is directed to desulfurization of a gaseous substrate.
2. Description of the Prior Art
It is well known in the performance of gas phase reactions to heat up the reactant gas mixture to the reaction temperature by regenerative heat exchange with hot exit gas after the reaction. The combination of gas phase reaction with regenerative heat exchange, which is also denoted unstationary-state process, is, in particular, advantageous compared to the use of recuperative heat exchange, such as a shell-and-tube heat exchanger, in processes in which the adiabatic temperature increase caused by the reaction is smaller than about 25% of the increase in temperature required to heat up the inlet gas to the reaction temperature. This is because regenerative heat exchangers usually are less expensive than recuperative heat exchangers when the thermal heat exchange efficiency is higher than 75%.
Thermal efficiency up to 98% is typically achieved in regenerative heat exchange, which cannot be achieved practically by recuperative heat exchange. DK Patent Application No. 0375/77 and Yu. Sh. Matros in "Catalytic Processes under Unsteady State Conditions", Elsevier, Amsterdam/New York, 1989, disclose examples on use of regenerative heat exchange combined with reactions such as catalytic oxidation of SO.sub.2 or combustible components in off gases in which the adiabatic temperature increase by the oxidation reactions are from a few degrees up to 100-200.degree. C. In known applications in which SO.sub.2 is oxidized into SO.sub.3, the process gas is free of H.sub.2 O and H.sub.2 SO.sub.4 -vapor in order to avoid condensation of sulfuric acid in the regenerative heat exchanger.